Arcuate shaped composites of refractory tapes embedded in a metal matrix

ABSTRACT

COMPONENTS, SUCH AS AIRFOILS FOR JET ENGINES AND OTHER COMPLEX SHAPED PARTS, ARE PROVIDED BY FIBER-REINFORCED, HIGH-STRENGTH, LIGHT-WEIGHT METAL MATRIX COMPOSITES ECOMOMICALLY PREPARED TO CLOSE DIMENSIONAL TOLERANCES BY APPLYING MATRIX TAPES IN SIDE-BY-SIDE RELATION TO A CONTOURED METAL BASE SHEET OR FOIL AND BUILDING UP A BODY OF THE DISIRED THICKNESS AND SHAPE WITH SUPERIMPOSED LAYERS OF SUCH APPLIED TAPES, WHICH ARE THEN COVERED WITH A CONTOURED METAL COVER SHEET OR FOIL. EACH LAYER MAY BE BONDED TO THE UNDERLYING LAYER BY RESISTANCE DIFFUSION BONDING, AND THE COVER SHEET IS BONDED TO THE BASE SHEET PRIOR TO HOT PRESSING THE ENTIRE ASSEMBLY TO THE FINISHED SIZE AND SHAPE. THE TAPES ARE PREFERABLY COMPOSED OF REFRACTORY FILAMENTS, SUCH AS BORON, RUNNING LENGTHWISE, AND EMBEDDED IN A METAL MATRIX WHICH IS FULLY CONSOLIDATED. THE METAL MATRIX AND BASE AND COVER SHEETS ARE PREFERABLY COMPOSED OF ALUMINUM OR TITANIUM ALLOYS, AND THE INTERIOR OF THE COVERED ARTICLE IS PREFERABLY EVACULATED PRIOR TO PRESSURE BONDING.

March 14, 1972 j ALEXANDER 6,649,425

AHUUA'L'L'. sEArED COMPOSITES OF REFRACTORY TAPES EMBEDDED IN A METAL MATRIX Filed March 18, 1970 dkzzj/ilamflder BY h United States Patet 3,649,425 ARCUATE SHAPED COMPOSITES OF REFRAC- TORY TAPES EMBEDDED IN A METAL MATRIX John A. Alexander, Painesville, Ohio, assignor to TRW Inc., Cleveland, Ohio Filed Mar. 18, 1970, Ser. No. 20,551

Int. Cl. 1332b 15/14 U.S. Cl. 161-43 5 Claims ABSTRACT OF THE DISCLOSURE Components, such as airfoils for jet engines and other complex shaped parts, are provided by fiber-reinforced, high-strength, light-weight metal matrix composites economically prepared to close dimensional tolerances by applying matrix tapes in side-by-side relation to a contoured metal base sheet or foil and building up a body of the desired thickness and shape with superimposed layers of such applied tapes, which are then covered with a contoured metal cover sheet or foil. Each layer may be bonded to the underlying layer by resistance diffusion bonding, and the cover sheet is bonded to the base sheet prior to hot pressing the entire assembly to the finished size and shape. The tapes are preferably composed of refractory filaments, such as boron, running lengthwise, and embedded in a metal matrix which is fully consolidated. The metal matrix and base and cover sheets are preferably composed of aluminum or titanium alloys, and the interior of the covered article is preferably evacuated prior to pressure bonding.

BRIEF SUMMARY OF THE INVENTION Heretofore, complex, composite shapes or parts, such as jet engine fan blades, were made from laminae cut to predetermined pattern size and shapes, stacked according to pattern, and then consolidated by hot pressing. These methods result in large wastage of material and involve a consolidation operation with a substantial reduction in volume of the stacked laminae. When the laminae were composed of resin-bonded, fiber-reinforced sheets, the reinforcing filaments would be shifted in uncontrolled, random fashion.

The present invention avoids the objections of prior known methods and produces stronger and more accurately shaped composites by building up the body of the component or part from tapes laid edge to edge and layer upon layer on a countoured sheet until the desired shape is obtained. The fully consolidated tapes or strips are laid down by resistance bonding so that the filaments cannot shift on later pressure bonding, A roller is preferably used to resistance bond the tapes. The cover sheet is placed over the built-up body of tapes and is welded to the base sheet to form a complete envelope which is then evacuated, and the whole assembly is placed in a hot pressure die for final consolidation. The final consolidation operaiton only slightly reduces the volume of the body, in the range of about 2 to 5%, and no adverse shift of the filaments can occur.

It is then an object of this invention to provide composites with body portions composed of a plurality of layers of refractory tapes, with each layer composed of a plurality of tapes in side-by-side relation.

Another object of this invention is to provide jet engine fan blades with body portions composed of metal matrix reinforced tapes in side-by-side and layer-by-layer relation and covered with a metal sheath,

Another object of this invention is to provide composites of accurate shape, high strength, and low density having body portions composed of layers, with each layer formed from a plurality of tapes in side-byside relation.

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Another object of this invention is to provide an economical method of producing composite shapes avoiding the use of heretofore required complex-shaped, precut laminae.

Another object of the invention is to provide a method of making composites of accurate shape, high strength, and light weight from tapes.

A further object of the invention is to provide a method of making filament-reinforced composites without shifting the filaments during consolidation of the constituents.

A further object of this invention is to provide a method of making composites with a minimum reduction in volume of the constituent materials.

Other and further objects of this invention will become apparent to those skilled in this art from the following detailed description of the annexed sheet of drawings which, by way of a preferred embodiment only, illustrates one example of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a jet engine fan blade in an initial stage of formation according to this invention:

FIG. 2 is a magnified, fragmentary perspective view of a fiber-reinforced tape used in making composites according to this invention;

FIG. 3 is a transverse cross-sectional view of a turbine fan blade on a contoured die just before final consolidation by heat and pressure according to this invention;

FIG. 4 is a perspective view of a turbine fan blade after complete assembly according to this invention, but prior to final consolidation;

FIG. 5 is a transverse sectional view of the blade of FIG, 4 illustrating the manner in which flash is out therefrom; and

FIG. 6 is a perspective view of a finished turbine fan blade according to this invention.

DETAILED DESCRIPTION OF THE PREF-EERED EMBODIMENT In FIG. 1 of the drawing there is shown a contoured mandril or die 2, the surface of which has the shape of one face of the turbine fan blade or other article to be formed. Supported on the surface of the mandril 2 is a metal base sheet 4 contoured to match the surface of the mandril. The material from which this sheet 4 is made will depend on the service for which the composite is to be used. For example, if the article is to be an airfoil for pet engine fan blades, the sheet may be aluminum alloy or titanium. On the other hand, if the airfoil is to be used as a turbine bucket subject to excessive heat, the covering sheet may be made of heat-resistant material such as titanium, stainless steel or other refractory metal or alloy.

As also shown in FIG. 1, flexible, consolidated, fiberreinforced metal matrix tape 6 is fed from a tape supply reel 8 to the contoured surface of the base sheet 4. As each strip of tape is laid on the surface of the sheet, it is diffusion bonded to this sheet by means of a resistanceheated bonding roller 10. The tapes are laid side-by-side and layer-upon-layer until a stack of the desired shape and contour is built up. If desired, the tapes may also be laid diagonally or crosswise (transversely) and successive layers of the tapes may have the fibers cross-plied. The bonding roller 10 bonds each tape to the tape below thereby preventing shifting of fibers and compacting the assembly to avoid the bulk of heretofore stacked resinbonded laminae. Since the tape is laid side-by-side to form the desired shape of each layer, wastage of material is avoided and close dimensional tolerances are maintained.

The width of the tape 6 may vary, depending on the degree of twist and camber associated with the specific airfoil or other article being formed. Widths of from /s to 1 inch are feasible, with wider tapes being useful where the twist and camber of the article is not appreciable. The tape may contain 25 to 60 volume percent of filament having a diameter of about 4 to 8 mils. Where 4 mil filament is used the tape may have a thickness of 5 mils. Where 8 mil filament is used, the tape may be 8 to 10 mils in thickness.

The preferred tape 6 is a fiber-reinforced metal matrix composition prepared as shown and described in an article by John A. Alexander, the inventor named in this application, on pages 58-63 of the July 1968 issue of Materials Engineering, which is incorporated herein by reference. As therein disclosed, metal matrix tapes are prepared by electro deposition or by chemical vapor deposition or by plasma spray deposition of the metal on filaments of refractory materials such as boron, boron silicon carbide, or silicon carbide. The tapes 6 may be composed of one or more layers of filaments 6a sandwiched in the matrix 6b. As shown in FIG. 2 the filaments 6a are in a mono-layer arrangement and run lengthwise of the tape, with the filaments spaced side-by-side and embedded in metal matrix 61;. However, the tape may contain more than one filament layer. As illustrated in FIG. 3, a body 12 is built up from the tapes 6 on the base sheet 4 to provide the desired thickness and contour of the article being formed. As also shown, the base sheet 4 extends beyond the die or mandril 2. A cover sheet 14, preferably of the same material as the base sheet 4, is then laid over the body 12, with margins of the sheet extending therebeyond to cover the margins of the base sheet 4 as illustrated. These sheets preferably have a thickness of about .010 to .012 inch. A top mandril or die 16 contoured to the shape desired for the top face of the article being formed is pressed against the sheet 14 over the body 12. The margins of the base sheet 4 and cover sheet 14 extend beyond the mandrils 2 and 16 and are welded together at 18 to form a sealed envelope around the body 12 except for a small hole or opening 20 in one end of the assembly, as shown in FIG. 4. The body 12 is thus sheathed in a sealed envelope, which is then evacuated through the opening 20 to remove air and prevent oxidation in the envelope during final bonding and consolidation. The hole 20 is sealed after the envelope is sufficiently evacuated.

Since the body 12 is composed of consolidated tapes 6 which themselves are partially consolidated by the diffusion bonding during the building up of the body on the base sheet 4, final consolidation of the assembly in the die press between the mandrils or dies 2 and 16 occurs with only a small decrease in volume of the assembly, thereby further protecting against shifting of filaments 6a.

Where the material of the cover and base sheets and the matrix metal is a high melting material, such as titanium, the bonding for final consolidation is carried out at temperatures of about 1650 to 1800 F., and at pressures of from 12,000 to 15,000 pounds per square inch. Where the metal or alloy of the cover foils and matrix metal is lower melting, such as an aluminum alloy, the diffusion bonding may be carried out at temperatures 4 of 900 to 1100 F. and pressures of from 4,000 to 9,000 pounds per square inch.

After the bonding operation, as shown in FIG. 5, the welded-together edges of the base and cover sheets 4 and 14 are trimmed off as flash 22.

As shown in FIG. 6, a finished airfoil 24 of this invention has a complete envelope or sheath 25 completely encasing a consolidated interior body '26, with the filaments 6a in the body extending lengthwise of the airfoil.

It will be appreciated that many different types of filaments can be used in the tapes and that refractory materials are highly desired for turbine engine components. Likewise, various metals and alloys such as aluminum, titanium, stainless steel, super alloys, such as disclosed in U.S. Pats. Nos. 3,005,705, 3,526,499 and 3,146,136, and other refractory metals can be used as the matrix metal.

The method of this invention can be performed under control of a computer program providing for tape sup ply and advance, bonding, welding, and shearing. The method of the invention eliminates waste and reduces the number of steps required by heretofore necessary matwinding and foil-forming. Decomposition of binder is avoided by providing fully consolidated tapes assembled and held together for direct insertion into the final diffusion pressure-bonding dies.

I claim as my invention:

1. A composite article comprising a shaped body having a plurality of layers of fiber-reinforced metal matrix tapes in side-by-side relation and difiusion-bonded to each contiguous layer, and a sheath of thin metal encasing and diffusion-bonded to said body.

2. The article of claim 1 wherein the tapes have fiber filaments running lengthwise thereof.

3. The article of claim 1 wherein the fibers of the tapes are composed of material selected from the group of boron, boron-silicon carbide, and silicon carbide, and the metal matrix is composed of a metal or metal alloy selected from the group consisting of aluminum, titanium, stainless steel and super alloys.

4. The article of claim 1 wherein the article is contoured to the shape of an airfoil structure.

5. The article of claim 4 wherein the metal of the tapes and sheath is titanium.

References Cited UNITED STATES PATENTS 3,098,723 7/1963 Micks 29-1568 B 3,471,270 10/1969 Carlson 29-191 X 3,574,040 4/1971 Chitwood et al. 156-213 3,567,407 3/1971 Yoblin 244-123 3,093,352 6/ 1963 Hoft'strom 244-1102 3,416,756 12/1-968 Windecker 244-123 3,466,219 9/1969 Schwartz 161-143 X 2,938,821 5/1960 Nack 156-180 X 3,091,262 5/1963 Donaldson 161-143 X FOREIGN PATENTS 231,038 6/1959 Australia 161-143 PHILIP DIER, Primary Examiner U.S. Cl. X.R. 

